In recent years, see-through displays have been receiving attention as display devices for information displays and digital signage. In the see-through displays, the background scene (the rear surface side of the display panel) can be seen through, and therefore, information can be displayed on the display panel in such a manner that the information is superimposed on the background scene. This technology can realize a novel representation which cannot be realized by conventional display devices. Thus, the see-through displays are excellent in customer appeal and eye-catching effects. Meanwhile, uses of the see-through displays in showcases and show windows have been proposed.
When a liquid crystal display device is used as a see-through display, its low light utilization efficiency is a bottleneck. The low light utilization efficiency of the liquid crystal display device is attributed to color filters and polarizers which are included in common liquid crystal display devices. The color filters and polarizers absorb light in a particular wavelength band and light of a particular polarization direction.
In view of the above, using a field sequential type liquid crystal display device is considered. According to the field sequential method, a color display is performed by switching the color of light emitted from an illuminator unit for irradiation of a liquid crystal display panel in a time division manner. Therefore, the color filters are unnecessary, so that the light utilization efficiency improves. Note that, however, the field sequential method requires the liquid crystal display device to have high responsiveness.
Patent Documents 1 and 2 disclose liquid crystal display devices which include an electrode structure that is capable of alternately producing a longitudinal electric field and a transverse electric field across the liquid crystal layer, thereby achieving improved response characteristics. In the liquid crystal display devices disclosed in Patent Documents 1 and 2, a longitudinal electric field is produced across the liquid crystal layer at either of a transition from the black display state to the white display state (rising) and a transition from the white display state to the black display state (falling), and a transverse electric field (fringe electric field) is produced across the liquid crystal layer at the other transition. Therefore, a torque produced by application of the voltage affects liquid crystal molecules at both rising and falling, so that excellent response characteristics can be achieved.
Patent Document 3 proposes a liquid crystal display device in which high responsiveness is achieved by such an arrangement that an alignment regulating force produced by an electric field acts on liquid crystal molecules at both rising and falling.